Thanks for replying! Kerbal space program IS focused on space, but it is also focused on exploration. There are a few Easter eggs on kerbin, after all. Hydrodynamics are not that different than aerodynamics. Water is just heavier, that's all. It should not take that much memory if you slightly merge the two systems. Think of it as a Y. The bottom part is the simmularity, and the split is where the system factors in the differences, like weight. Also, a couple of new, specialized parts won't hurt.